This invention relates to a placement instrument for dental prosthetic devices. More particularly, it relates to an instrument for use in holding, matching, fitting and placing dental prosthetic devices in an efficient and time-conserving fashion.
In recent years, the use of dental prosthetic devices for both therapeutic and cosmetic purposes has greatly increased. Dental veneers, used to cover or cap a surface of a patient's disfigured or discolored tooth, are virtually unnoticeable when applied, and create a seemingly new tooth for the patient. Because the process of applying such a prosthesis is tedious and time consuming, however, dentists have been forced to work in ways which are both awkward and inefficient.
A dental veneer is applied to a patient's tooth by a dentist through a series of steps. The veneer, which conforms to the size, shape and color of the patient's tooth, is commonly a porcelain laminate selected from stock forms or manufactured by a laboratory from an impression of the patient's tooth.
Once the dentist has selected or received the correct veneer, and fitted and matched it to the tooth, the tooth and the veneer are readied for application. Typically, the dentist prepares both the tooth and veneer with an acid etching agent, applies a bonding agent to the etched surfaces, and puts the veneer in place. The bonding agent is then cured, typically by certain spectra of light which react with the bonding agent, after which the veneer is securely held in place by the bonding agent and the structural stability of the tooth. Then the dentist may file and polish the veneer.
The steps of selecting, sizing, fitting and fixation of the veneer to the tooth are time-consuming and cumbersome procedures which require that the veneer be mounted on the tooth several times. First, the dentist must be sure that the porcelain veneer material matches the color of the patient's teeth, a step which in itself may take several placements. In addition, since the dental veneer must conform exactly to the shape and size of the tooth which it will cover, the dentist must perform a number of trial fittings so as to insure a proper match. During these steps it is important to isolate the area where the veneer will be placed so not to contaminate the veneer and the tooth with foreign objects, such as saliva and food particles. Only after matching the size, fit and color of the veneer does the dentist place the veneer on the tooth for permanent application. This, as mentioned, is done with light-curable bonding agents which do not harden until exposed to certain spectra of light, thus allowing the dentist some additional time to move the veneer to its final location.
Currently, the dentist accomplishes each of these placement steps by using fingers or a dental instrument employing an adhesive or suction to hold the veneers. Unfortunately, both the manual and instrument-aided methods currently used can cause a number of problems for the dentist during the veneer fitting and application process.
When the manual method is used, if the fragile prosthesis slips and falls out of the dentist's fingers, it may be permanently damaged. Likewise, the veneer may break if the dentist applies too much pressure during placement. When the veneer is adjusted to assure a correct esthetic match and functional fit, the dentist is required to continually touch and move the veneer by hand, thus increasing the risk of contamination to the veneer and bonding agent. Finally, the dentist's fingers can shadow the light used to cure the bonding agent, thus causing an uneven bond and allowing microcavities to develop which adversely affect long-term adhesion.
The current instrument-aided methods available for applying dental veneers also cause problems. First, if the dentist uses a prior-art adhesive system to place the veneer, the adhesive between the instrument and the veneer frequently sticks to the veneer and subsequently must be removed by hand. Secondly, when the dentist permanently places the veneer using a prior-art adhesive system, subsequent withdrawal of the instrument may cause the adhesive to pull on the veneer and thus dislodge it.
Suction-type instruments have also been used for placing dental prostheses, but they require frequent removal and replacement of various nozzles and adaptors, thus increasing the risk of contamination. In addition, if the suction from such an instrument is not continuously and uniformly applied to the veneer, the latter may slip and drop during application, leading again to damage and contamination.
Accordingly, there is a need for an improved instrument to manipulate, fit and place a dental veneer on a patient's tooth. In attempting to fill this need, the present invention provides an improvement on prior-art adhesive systems, and in particular it provides a multi-adhesive system. While the use of adhesive materials for this purpose is not in itself novel, prior-art adhesive devices have not completely solved the problem of how to release a dental veneer without dislodging it after the adhesive has served its purpose of transporting the object to its final destination, and the problem of how to avoid leaving behind a residue of adhesive material when the job is finished.
FIGS. 1-7 of Seidler U.S. Pat. No. 4,073,530 disclose two embodiments of a small-object pick-up and manipulating device comprising a handle portion and a flexible metal pick-up portion which is apparently permanently coated with a pressure-sensitive adhesive layer. This adhesive layer is covered by a protective release paper which is removed before picking up a small object. After the small object is picked up and placed elsewhere, the pick-up portion is mechanically flexed and rotated to accomplish a rolling action which helps to separate the small object from the adhesive on the pick-up device. So long as the adhesive coating remains in place, however, this type of device is unsuitable for autoclaving and thus could not safely be reused in a dental environment. It also employs a broad metal tip which would cast too large a shadow during light-curing of the bonding agent.
FIGS. 8-10 of the Seidler patent disclose a somewhat different device employing a flexible pick-up tip formed of an elastomeric material which also has the capability of performing a rolling action when the small object is released. This elastomeric tip further complicates the problem of autoclaving in a dental environment, since most elastomeric materials do not withstand high temperatures.
In FIGS. 11 and 12 of Seidler it is suggested that a reservoir of adhesive material be provided at the tip of the instrument, instead of a thin layer. This embodiment is also unsuitable for autoclaving, because the adhesive material cannot withstand high temperatures either.
Brown U.S. Pat. No. 4,953,902 is specifically directed to the dental veneer applicator art, and like FIGS. 11 and 12 of Seidler above, it also employs a reservoir of adhesive material. Brown discloses an elongated handle having a plunger and cylinder forming a chamber to hold the adhesive material. Pressure on the handle allows the plunger to extrude a small portion of the adhesive material onto the veneer so that the instrument may pick up and place the veneer. The veneer is then secured to a tooth with a bonding agent. There is no discussion in Brown, however, of the problem of sterilization after use and how that problem is affected by the presence of left-over adhesive material in the chamber.
Nussbaum U.S. Pat. No. 4,834,654 discloses a dental prosthesis applicator comprising an elongated flat handle and a flexible adhesive strip. The adhesive strip is covered by a protective shield which is removed before use, thus exposing an adhesive surface. The prosthesis adheres to the adhesive surface, thereby allowing the dentist to place the prosthesis onto a tooth. A bonding agent between the prosthesis and the tooth is used for permanent placement. The handle and the adhesive strip are both quite broad, and must be made of transparent material to avoid shadowing the prosthesis during the curing process.
The problem of autoclaving is not mentioned in Nussbaum, and it may well be a disposable device since it is made of plastic. Reusable instruments are less expensive than disposable ones over the long run, however, and are also ecologically more desirable because they do not intensify the problem of waste disposal. In viewing the dental prosthesis during the matching and fitting steps, moreover, a dentist who uses the Nussbaum applicator is forced to look through the transparent material and therefore may not get a clear view, especially for the purposes of color matching.
Oliva U.S. Pat. No. 5,040,981 also discloses a device for manipulating dental prostheses. FIGS. 1, 2, and 4 disclose embodiments of the device comprising an elongated cylindrical handle terminating in an elongated tip support section and a concave tip. The tip sections are disposable items constructed from plastic or stiff paper. Although the tip surfaces are directly coated with adhesive, clean-up and sterilization of the tip is not mentioned. This limits the use of each tip section to only one patient. As previously noted, disposable devices are more expensive in the long run, and more damaging to the environment.
The Oliva device also presents a problem regarding the application of the adhesive. If the tips are not pre-coated, the adhesive must be applied by spraying, or by dipping the tip into an adhesive. This can be a messy and time-consuming job, and there is some danger that the reservoir of adhesive may become contaminated while it is left open during the procedure. Additionally, the tip section of the instrument may become contaminated when it is handled by the user's fingers while being placed onto the reusable handle.
The tips of the Oliva device are flat or concave, which is disadvantageous because not all veneers are the same shape, and because a flat or concave tip does not aid in the removal of the tip and the adhesive from the prosthesis.